Presumably attracted by the light a large number of Cydnid bug, Aethus indicus, invaded into the houses in a town on Okinoerabu Island (37°30″N. 128°35″E) at about 8 pm. on July 18,1974. The invasion lasted for four nigths and occurred again August for five nights. The inhabitants were being afflicted with offensive smell emitted by the bugs and suffered from the contamination of food and drink with their stink fluid. In addition, 76 cases of earache caused by the entry of the bug should been treated by local clinics. Similar outbreak of cydnid bug and earache cases were recorded simultaneously from two adjacent islands, Tokunoshima and Yoron. The cases of the earache were 35 as reported from these two islands.